The present invention relates to methods of and apparatus for encoding and decoding digital data for transmission, recording or reproduction and, more particularly, to encoding and decoding digital data for representation in a video frame.
In video recording applications, it is frequently desirable to record digital data onto the same recording medium on which video image data are recorded. As an example, in the recording of video images acquired during a medical diagnostic procedure, text data identifying the patient tested and the time and date that the procedure was performed are often recorded with the video images.
The data may be stored in the video frames that precede the frames in which the video images are stored. As an example, text data associated with a medical diagnostic procedure, such as during an angiography, are recorded up until the time that the irradiation source reaches full power, after which the images generated during the diagnostic procedure are subsequently recorded. The text data may be recorded by the steps of arranging text characters on a letter board, irradiating the letter board, receiving the image of the letter board and then recording the image in plural video frames on a recording medium.
This conventional recording method has the drawback that only a small number of text characters can be arranged on a letter board for storage in the video frames and has the further drawback that the same text characters are stored in each of the frames.
Alternatively, the data may be stored in the same video frames in which the video images are stored such as by overlaying a portion of the video image with text characters, thereby obscuring a portion of the video image. If a large number of text characters is stored in the frame, a significant portion of the video image is obscured, and, as in the example in which medical diagnostic images are recorded, the obscured area may be a potentially critical region of the video image. As a result, only a limited amount of text data may be stored in the video frame without concealing the video image.
To store greater quantities of data in conjunction with the video images, the additional data may be recorded on a separate storage medium, such as in a computer file or database. However, when the video images are displayed, the additional data must be accessed separately and cannot be easily displayed with the video images.